WebMD

There's a lot to explore at WebMD, including a drug and herb database, articles about diseases and conditions, information about clinical trials, and copious news and commentary relating to current events in the medical world. The site also presents live chats, offers newsletters on more than 35 subjects, assists users with finding doctors and health insurance, and provides the means for recording your medical profile and health history.

This is an ambitious site, replete with readable, accessible, and thorough information. It's a valuable resource, despite its somewhat obtrusive burden of advertising.